How do I detect if a certan sequence of elements is present in an array? E.g. if I have the arrays and needle
$needle = array(1,1);
$haystack1 = array(0,1,0,0,0,1,1,0,1,0);
$haystack2 = array(0,0,0,0,1,0,1,0,0,1);
How does one detect if the subset $needle is present in e.g. $haystack1? This method should return TRUE for $haystack1 and FALSE for $haystack2.
Thanks for any suggestions!
Join the arrays, and check for the strpos of the needle.
if ( strpos( join($haystack1), join($needle) ) >= 0 ) {
echo "Items found";
}
Demo: http://codepad.org/F13DLWOI
Warning
This will not work for complicated items like objects or arrays within the haystack array. This method is best used with itesm like numbers and strings.
If they're always a single digit/character then you can convert all elements to strings, join by '', and use the regex or string functions to search.
For the specific case where no array element is a prefix of any other element (when both are converted to strings) then the already posted answers will work fine and probably be pretty fast.
Here's an approach that will work correctly in the general case:
function subarray_exists(array $needle, array $haystack) {
if (count($needle) > count($haystack)) {
return false;
}
$needle = array_values($needle);
$iterations = count($haystack) - count($needle) + 1;
for ($i = 0; $i < $iterations; ++$i) {
if (array_slice($haystack, $i, count($needle)) == $needle) {
return true;
}
}
return false;
}
Disclaimer: There are ways to write this function that I expect will make it execute much faster when you are searching huge haystacks, but for a first approach simple is good.
